Spray coating apparatus for spraying liquid coating material under high pressure



' I June 22, 1965 K. H. LIEDBERG 3,190,554

SPRAY COATING APPARATUS FOR SPRAYING' LIQUID COATING MATERIAL UNDER HIGH PRESSURE Filed March 11. 1963 \T I I I 43,. 3 5 35 334732 5 5 3 4 I 26 38 23 [)3 35 40 1 1 15 36 212 211 3 30 Fig. 2 Z 28 Fig. 3

INVENTOR. KM RT l/semm Linus? Uited States Patent SPRAY C(DATlNG APPARATUS FOR SPRAYING lLlQUlll) COATING MATERKAL UNDER HIGH PRESURE Kurt Herman Liedberg, Shara, weden, assignor to Atlas Copco Alrtiebolag, Nacka, Sweden, a corporation of Sweden Filed Mar. 11, 1M3, Ser. No. 264,324 9Clairns. (61. 239578) This invention relates generally to a spray coating apparatus and more specifically to a spray coating apparatus for spraying liquid coating material under very high pressure in order to avoid the use of compressed air as an atomizing medium. The high pressure in airless spray coating guns, however, usually makes manual operation of the material control valve dimcult and is often responsible for a too slow opening movement thereof, which is apt to produce nonuniform splashed and unacceptable coatings.

Various attempts have been made to ease and accelerate operation of the liquid coating material control valve, but these efforts have been unsatisfactory particularly because of the constructional complications in volved.

It is a primary object of the invention to provide a spray coating apparatus for spraying liquid under high pressure by the aid of a simple and comparatively cheap mechanism in which the force required for operation of the liquid control valve is eiiiciently reduced. Another object of the invention is to provide a spray coating apparatus of the above character in which in the closed position of the control Valve pressure differences acting on said valve are fully balanced. A f-urtherobject of the invention is to provide a spray coating apparatus of the above character in which in the open position of the control valve pressure differences acting on said valve are kept at a minimum by the use of a valve stem of extreme slenderness.

A still further object of the invention is to provide a spray coating apparatus of the above character in which a very small longitudinal movement of the control valve is necessary for a maximum valve opening even though there is only very small displacement of the valve body in the opening direction, whereby the tendency of splash marks to appear during opening or closing of the control valve is minimized or eliminated.

The above and other objects of the invention will become obvious from the following description and from the accompanying drawings, in which one embodiment of the invention is illustrated by way of example. It should be understood that this embodiment is only illustrative of the invention and that various modifications can be made within the scope of the claims without departing from the scope of the invention.

In the drawings FIG. 1 is a longitudinal sectional view through a spray coating apparatus according to the invention. FIG. 2 is an enlarged fragmentary view of the front portion of the apparatus in FIG. 1. P16. 3 is an enlarged sectional view on line 33 in FIG. 1. FIG. 4 is an enlarged sectional view on line 44 in FIG. 1 FIG. 5 is an enlarged sectional View on line 55 in FIG. 1.

Referring to the drawings, the spray coating apparatus or gun illustrated in FIG. 1 embodies a handle having a forwardly extending gun body 11, a trigger 12 being pivotally attached to the body by a pintle 13. Centrally in the body portion 11 there is provided a transverse through opening 14 from which there extends a traverse passage 15 of hexagonal cross section to the rear and forwardly directed bore 16, the passage 15 and the bore 16 being coaxial. The bore 16 communicates 3,19%,564 Patented June 22, 1965 with a counterbore 17 provided in the spray nozzle end of the body 11 and receives together with the bore 16 a stepped cylindrical housing 18, which is threaded internally at its forward end to receive a valve seat sleeve 19. The sleeve 19 has an internal annular shoulder 20 at its forward end which supports a valve seat 22 provided with a central discharge orifice 23 and having a press fit in the sleeve 19.

A deflecting plug 21 is fixedly connected to the forward end of the sleeve 19 as by threads and integral therewith. The plug 21 has a transverse jet spoiling surface 211 directly in front of the orifice 23 and a pair of through passages 212 which are disposed radially outwardly of the surface 211, the passages 212 converging in a point centrally in front of the deflecting plug 21.

A chamber 24 for coating liquid under high pressure is formed within the housing 18 and the sleeve 19, the chamber 24 being closed at its rear by a centrally perforated washer 27 resting against a shoulder in the housing 18 and pressed thereagainst by packing material 26 and a gland nut 25 threadedly received in the housing 18. A threaded passage 28 extends transversely to the counterbore 17 and receives a threaded connection 29 leading to a supply of coating liquid under high pressure, not shown. A tapered tip 30 on the connection 29 fits in a correspondingly shaped radial opening 31 through which liquid via the connection 29 may enter chamber 24, the tip 30 also being provided for keeping the housing 18 in place in the body 11. A locking screw 32 in the body 11 prevents removal of the connection 29.

The housing 18 has a threaded outward projection re ceiving a nut 33 thereon which secures a spray nozzle assembly to the forward end of the valve seat sleeve 19 and the plug 21. The assembly includes a centrally perforated washer 34 resting tightly against the sleeve 19 and a nozzle holder 35 which by a circumferential flange 36 thereon, engaged by an inner shoulder 37 on the nut 33, is affixed to the sleeve 19 and kept in firm engagement with the interposed washer 34. The holder 35 carries inside thereof a spray tip 38 having a small atomizing bore 39 formed axially therethrough and the tip 38 is kept in place against an internal shoulder in the holder 35 by a spacer sleeve 40.

A helical spring 43 bears against the washer 27 in the liquid chamber 24 and engages at its forward end a flange 44 on a guide member 45 extending inside of the spring 4-3 for a substantial length thereof. The guide member 45 is fixedly connected as by brazing to a slender valve stem 46 slidably projecting from the liquid chamber 24 to the rear through the washer 27, the packing material 26, and the gland nut 25. The slender stem 46 is a flexible steel wire such as a piano wire, for example having a diameter of l millimeter. The forward end of the guide member 45 is'th'readed and receives fixedly thereon a cylindrical control valve body 47 pro vided with a fiat front face for cooperation with the flat valve seat 22. The spring 43 exerts a closing bias on the valve body 47.

The passage 15 receives slidably and unrotatably therein an elongated hexagonal member or sleeve 49 internally traversed by the valve stem 46 which at its rear end is firmly engaged by a chuck 50. The chuck 50 has a tapered tip 52 incorporating longitudinal slits 521, FIG. 5, and is threadedly received in a hexagonal head 51 having a frusto-conical internal opening cooperating with the tip 52 for urging its slitted portions radially inward into firm engagement with the stem 46. The head 51 is slidably and unrotatably received in the passage 15. A helical spring 53 is interposed between guiding bores 54, 55 in respectively the head 51 and the sleeve 49, the spring 53 being weaker than the spring 43 in the liquid chamber 24.

The forward end of the sleeve 49 extends into the opening 14 and has a reduced cylindrical portion 56 which is received in a hole 66 centrally in a transverse plate 57. The trigger 12 straddles the body portion'11 and the opening 14 from below by spaced forked arms 58 having opposed slits 67 for receiving the ends of the transverse plate 57 whereby the plate 57 is movable in unison with the trigger 12. By pressing the trigger 12 the plate 57 and the sleeve 49 are displaced to the rear compressing the weak spring 53 until the sleeve 49 contacts the head 51. Continued movement of the trigger will force the head 51 rearwardly to open the control valve 47 through the medium of the stem 46.

For positively defining the throw of the sleeve 49, there is provided a locking mechanism including a ring 60 freely rotatable in atransverse through opening 61 in the body 11 around the sleeve 49. A pair of spaced circumferential grooves 62, 63 are provided in the mantle of the sleeve 49 adjacent the ring 60 and the sleeve 49 has also a flattened upper recess 68 extending between the groove .62, 63 and forming a communication therebetween. An abutment pin 64 traversing the ring 60 in its longitudinal central plane extends transversely over the recess 68. One end of the pin 64 has an outwardly projecting finger piece 65 formed thereon. With the abutment pin 64 in horizontal position and lying over the recess 68, i.e. the full line position of FIG. 3, the sleeve 49 by actuation of the trigger 12 is free to perform a full throw from neutral position with the pin 64 in the groove 63 at the rear end of the recess 68, which position corresponds to closed position of the control valve 47, to open position with the pin 64 in the groove 62 at the other end of the recess 68, in which position the control valve 47 is open, and back again to neutral position.

In many cases it is desirable to prevent actuation of the control valve 47 in closed as well as in open position thereof and in the illustrative apparatus this may be performed by selectively locking the sleeve 49 against axial movement in its neutral or open position. To this end the finger piece 65 may be pressed downwardly to turn the pin 64 from the recess 68 into one of the grooves 62 or 63 depending on the position of the sleeve 49. With the pin 64 engaging the groove 62, as shown in dotted lines in FIG. 3, the sleeve 49 is locked against axial movement in the retracted position of the head 51 and open position of the valve 47. Such position serves for producing a continuous spray without the operator having to depress the trigger 12. With the pin 64 turned into the groove 63 the sleeve 49 locks the trigger 12 in neutral position and such locking is advantageous as a safety measure during removal of the spray nozzle assembly or holder 35 for cleaning purposes.

A plunger 70 is axially movably arranged in the body 11 and engages frictionally the ring 60 against which the plunger 70 is pressed by a helical spring 71. The frictional engagement keeps the ring 60 and its pin 64 in the selected adjusted position.

In operation, high-pressure fluid from the source, not shown, is supplied via the conncfhon 29 to the liquid chamber 24. By pressing the trigger 12, the operator brings the sleeve 49 in contact with the head 51 and moves the sleeve and head in unison to the rear to open the control valve 47. Owing to the fiat surface of the valve face, the liquid, upon actuation of the valve body 47, will practically instantly be supplied to the discharge opening 23 and on via the passages 212 in the deflecting plug 21 and the central opening of the washer 34 to the spray tip 38 at the desired velocity and pressure to produce effective atomization and spraying with a minimum of splashes. With the holder 35 removed the jet spoiling surface 211 of the deflecting plug 21 prevents unintentional direct outward projection of a massive high-energy jet from the orifice 23. Instead there will be formed two converging jets from the passages 212 combining their flow into a flattened spray of reduced velocity unable to cause injuries. The comparatively wide passages 212 do not disturb free flow to the spray tip 38 during normal operation of the apparatus. The central opening in the washer 34 is provided for suitably modifying the velocity of the flow to the spray tip 38. I

With the trigger 12 released the spring 43 will instantly close the control valve 47 and the spring 53 will thereupon move the sleeve 49 and the trigger 12 to neutral position. The spring 43 thus serves to produce a closing bias but is also active to prevent bucking of the slender flexible stem 46 under the high pressures of about 150-200 kilogrammes per square centimeter acting in the liquid chamber 24. The axial force to be balanced during opening of the control valve 47 depends on the pressure and the cross-sectional area of the stem and thanks to the slender stem this force will be small. As a consequence the spring 43 need not be strong and manual depression of the trigger 12 will therefore be quite easy. In order to fully relieve the control valve body 47 from axial forces when the control valve is closed, the discharge orifice 23 is given an area substantially equal to the cross-sectional area of the slender stem 46.

What I claim is:

1. In spray coating apparatus of the character described for spraying liquid coating material under high pressure and having a body with a liquid chamber, means for supplying coating liquid under high pressure to said chamber, a spray nozzle in communication with said chamber, and a discharge orifice between said chamber and said spray nozzle, the combination which comprises a fluid tight packing material seal forming the wall of said chamber opposite to said orifice, said seal having a restricted guide passage therethrough axially aligned with said orifice, a control valve reciprocable in said chamber for the opening and closing of said orifice and said nozzle to the flow of coating liquid from said chamber, a stern connected to said control valve at the end thereof opposite said orifice and slidably but tightly projecting through said guide passage for providing the sole support and movement of said control valve, trigger means connected to said stem to open said control valve, and spring means in said chamber surrounding said stem between said valve and said seal for biasing said control valve to close said orifice and for preventing buckling of said stem during reciprocation thereof.

2. A spray coating apparatus as set forth in claim 1 in which said control valve is a fiat faced surface type valve.

3. A spray coating apparatus as set forth in claim 1 in which said orifice and said stem are of substantially equal cross-sectional area.

4. A spray coating apparatus as set forth in claim 1 in which said stem is a piano wire.

5. In spray coating apparatus of the character described for spraying liquid coating material under high pressure and having a body with a liquid chamber, means for supplying coating liquid under high pressure to said chamber, a spray nozzle in communication with said chamber, and a discharge orifice between said chamber and said spray nozzle, the combination which comprises a fluid tight packing material seal forming the wall of said chamber opposite said orifice, said seal having a restricted guide passage therethrough axially aligned with said orifice, a control valve reciprocable in said chamber for the opening and closing of said orifice and said nozzle to the fiow of coating fluid from said chamber, a stem connected to said control valve at the end thereof opposite said orifice and slidably but tightly projecting through said guide passage for providing the sole support and movement of said control valve, trigger means connected to said stem to open said control valve, spring means in said chamber surrounding said stem between said valve and said seal for biasing said control valve to close said orifice and for preventing buckling of said stem during reciprocation thereof, and means disposed on said body and connected to said stem for locking said stem against movement with said control valve selectively in said open or closed position.

6. In spray coating apparatus of the character described for spraying liquid coating material under high pressure and having a body with a cylindrical liquid chamber, means for supplying coating liquid under high pressure to said chamber, a spray nozzle in communication with said chamber, and a discharge orifice disposed at one end of said chamber and communicating with said spray nozzle, the combination which comprises a control valve reciprocable in said chamber for the opening and closing of said orifice and said nozzle to the flow of coating fluid from said chamber, a stem connected to said control valve at the end thereof opposite said orifice for providing the sole support and movement of said control valve in said chamber, liquid chamber closure means disposed in said body on said chamber at the end thereof opposite said orifice, said closure means having a fluid tight packing material seal on one side thereof with a guide passage therethrough axially aligned with said orifice for providing easy access to said liquid chamber and the contents thereof, a stem connected to said control valve at the end thereof opposite said orifice and slidably but tightly projecting through said closure means for providing the sole support and movement of said control valve in said chamber, spring means in said chamber surrounding said stem between said valve and said closure means for biasing said control valve to close said orifice and for preventing buckling of said stem during reciprocation thereof, and means connected to said stem for the reciprocation thereof to open said control valve.

7. In spray coating apparatus of the character described for spraying liquid coating material under high pressure and having a body with a liquid chamber, means for supplying coating liquid under high pressure to said chamber, a spray nozzle in communication with said chamber, and a discharge orifice between said chamber and said spray nozzle, the combination which comprises a fluid tight packing material seal forming the wall of the chamber opposite said orifice, said seal having a restricted guide passage therethrough axially aligned with said orifice, a control valve reciprocable in said chamber for the opening and closing of said orifice and said nozzle to the flow of coating liquid from said chamber, a stem connected to said control valve at the end thereof opposite said orifice and slidably but tightly projecting through said guide passage for providing the sole support and movement of said control valve, a bore disposed in said body outside said chamber and axially aligned with said stern, an elongated member axially movably disposed in said bore and engaging said stem, first spring means in said chamber surrounding said stem between said valve and said seal for biasing said control valve to close said orifice and for preventing buckling of said stern during reciprocation thereof, trigger means connected to said elongated member for the movement thereof and for reciprocation of said stem, second spring means weaker than said first spring means and disposed between said trigger means and said elongated member for biasing said trigger means in a closed position, and means disposed in said body and connected to said elongated member for the selective locking thereof against movement in said bore in said open and said closed position.

8. A spray coating apparatus for spraying liquid coating material under high pressure of the type in which a removable and exchangeable spray nozzle is provided with an atomizing aperture for forming a jet of liquid particles and in which a control valve positioned in proximity to and upstream of said aperture and in alignment with said spray nozzle controls the flow of coating material under high pressure through a restricted discharge orifice in the seat of said control valve to said aperture, comprising in combination therewith a valve seat sleeve for supporting said valve seat, a deflecting member integral with said sleeve and disposed between said seat and said spray nozzle, a jet spoiling surface on said deflecting member and disposed transversely in front of said orifice for preventing unhindered outward projection of a massive jet from said orifice with said spray nozzle removed, and passage means in said deflecting member and radially offset from said orifice for maintaining outward flow past said deflecting member.

9. A spray coating apparatus as set forth in claim 8, in which said passage means are a pair of passages converging in a point downstream of said deflecting member.

References Cited by the Examiner UNITED STATES PATENTS 1,551,508 8/25 Smith 251-294 2,550,888 5/51 Traughber 239414 2,557,606 6/51 Liedberg 239414 2,621,970 12/52 Dalrymple 239408 2,705,663 4/55 Gilbreath 239-583 2,956,752 10/60 Wahlin 239583 2,969,926 1/61 Peeps 239-407 2,991,940 7/61 Dupler et al. 239583 3,000,576 9/61 Levey et al. 239-583 3,116,020 12/63 Rosen et al. 239--578 EVERETT W. KIRBY, Primary Examiner. 

1. IN SPRAY COATING APPARATUS OF THE CHARACTER DESCRIBED FOR SPRAYING LIQUID COATING MATERIAL UNDER HIGH PRESSURE AND HAVING A BODY WITH A LIQUID CHAMBER, MEANS FOR SUPPLYING COATING LIQUID UNDER HIGH PRESSURE TO SAID CHAMBER, A SPRAY NOZZLE IN COMMUNICATION WITH SAID CHAMBER, AND A DISCHARGE ORIFICE BETWEEN SAID CHAMBER AND SAID SPRAY NOZZLE, THE COMBINATION WHICH COMPRISES A FLUID TIGHT PACKING MATERIAL SEAL FORMING THE WALL OF SAID CHAMBER OPPOSITE TO SAID ORIFICE, SAID SEAL HAVING A RESTRICTED GUIDE PASSAGE THERETHROUGH AXIALLY ALIGNED WITH SAID ORIFICE, A CONTROL VALVE RECIPROCABLE IN SAID CHAMBER FOR THE OPENING AND CLOSING OF SAID ORIFICE AND SAID NOZ- 